The long-range goal of the proposed research is to understand the mechanisms of enzymatic synthesis of DNA. Specific emphasis is placed on the characterization and labeling of the sites responsible for substrate binding and template binding. Reagents have been developed for specific labeling of the active site regions responsible for substrate binding (Pyridoxal phosphate) and template binding (Phenylglyoxal). In addition, kinetic studies are expected to clarify the nature of involvement of other reactions as well as structural components of DNA polymerases.